I've found the following references to be invaluable in understanding tramway company history, the intricacies of civic coats of arms, what is actually out there in terms of tramway uniform buttons, and the origins of the London Underground/Transport 'bullseye' logo.
Tramway company history:
'The Directory of British Tramways - Every Passenger-Carrying Tramway, Past and Present', Keith Turner; Patrick Stephens Limited (1996). ISBN 1 85260 549 9.
This book is the seminal work on British tramway systems, containing detailed accounts of the histories, working and stock of over 350 lines and systems. RRP is £24.99, however, secondhand copies are reasonably easy to obtain for around £10.00. Try 'Abebooks' secondhand book search - click on this link to go to Abebooks. Note that this work is currently in the process of being updated as separate regional volumes, the following of which are currently available (RRP £19.99):
'The Directory of British Tramways; Volume 1 - Southern England and the Channel Islands', Keith Turner; Tempus Publishing Limited (2009). ISBN 978 0 7524 3901 3.
'The Directory of British Tramways; Volume 2 - Central England, Wales and Ireland’, Keith Turner; The History Press (2007). ISBN 978 0 7524 4233 4.
'The Tram Book’, Paul Collins; Ian Allan Publishing (1995). ISBN 0 7110 2268 2.
An informed but very readable and excellently illustrated account of the history and development of the tramway in the United Kingdom. Currently out of print, but relatively easy to obtain second hand for around £10.00.
'Civic Heraldry of England and Wales'.
Robert Young's extremely impressive web site containing descriptions and images of approaching 1000 local authority heraldic designs, both current and obsolete. Basically, everything you wanted to know about armorial devices, as well as translations of the latin mottos that frequently appear on tramway buttons. Click on the following link to go to the Civic Heraldry website.
Three issues of ‘Button Lines’ - the Journal of the British Button Society (ISSN 0309-121X) - contain articles by Alan R Williams on tramway buttons of the UK and Ireland. Back copies of these issues can be obtained by contacting the British Button Society, who will let you know who to write to. Back issues usually cost either £2.50 (B&W) or £3.50 (Colour). Click on the following hypertext link to go to the British Button Society's home page web site. The releavant issues are:
'Tramway Buttons of the British Isles - Part One'', Alan R Williams. Button Lines, Issue 113 (December 2002): p10-13. Contains brief descriptions and photos of Accrington (No 1) through to Lytham St Annes (No 45).
'Tramway Buttons of the British Isles - Part Two'', Alan R Williams. Button Lines, Issue 114 (March 2003): p8-11. Contains brief descriptions and photos of Manchester (No 46) through to Bradford (No 82), as well as details of other buttons known to exist (no photos).
'Tramway Buttons of the British Isles - First Update'', Alan R Williams. Button Lines, Issue 116 (September 2003): p13. Short update adding four new buttons (Nos 83 to 86) and additional information on buttons in Parts One and Two.
The London Underground/Transport 'bullseye':
'A Logo for London'. David Lawrence; Capital Transport Publishing (2000). ISBN 185414 232 1.
This books charts the origins and subsequent development of the iconic London Underground bar and circle logo, historically referred to as the 'bullseye' ('roundel' post 1972). This device was first used by the Underground Electric Railways of London Limited, and was eventually disseminated across various companies within that group - including London United Tramways, Metropolitan Electric Tramways and South Metropolitan Electric Tramways - finally being adopted by London Transport.